food tests

• Reagent


  A chemical that indicates the presence of a substance, usually by changing colour
• Testing for reducing sugar


  1. Add Benedict's reagent to the food and boil in a water bath

  2. Initial colour: Blue

  3. Colour of positive result: Brick red precipitate
• Testing for starch


  1. Add iodine reagent to the food

  2. Initial colour: Yellow-brown

  3. Colour of positive result: Blue-black
• Testing for protein/amino acids

  1. Add Biuret reagent (a mixture of sodium hydroxide and copper sulfate) to the food

  2. Initial colour: Blue

  3. Colour of positive result: Lilac/purple
• Testing for fat

  1. Add ethanol to the food to dissolve the fat then add water

  2. Initial colour: Colourless

  3. Colour of positive result: White emulsion